The present invention relates to superconducting circuits, and more specifically, to multi-tunable superconducting circuit system.
Superconducting circuits have experienced notable advances over the last few decades, finding numerous applications in nanotechnology. From extremely sensitive magnetometers to microwave amplifiers, photon detectors or qubits for quantum information processing, these devices offer an enormous versatility. For quantum computation, in particular, superconducting qubits in the circuit Quantum Electrodynamics (QED) architecture have proven very successful. In this architecture, one or more qubits are coupled to one or more resonators, which can act both as mediators of the coupling between the qubits and as readout elements. For systems with only a few qubits and resonators, the interaction between them does not need much tunability. As the size of the system grows, however, the ability to independently tune the coupling strength between different parts of the device becomes critical for the implementation of quantum algorithms.
Several coupling schemes between two superconducting qubits and between one superconducting qubit and one resonator have been implemented over the years. However, no solution has been given to the problem of coupling one qubit to two resonators with independent tunability of the coupling to each of the resonators. Most tunable coupling schemes in superconducting circuits realized to date have been designed to tune the coupling between qubits. In these implementations, the coupling between the qubits has mainly been achieved by non-linear inductances and most of the designs give the ability to control both the magnitude and the sign of the coupling.
Several solutions exist to couple qubits and resonators. One example is an RF SQUID in the non-hysteretic regime to couple a lumped element resonator to a phase qubit. Another example is a modified transmon with an extra degree of freedom in order to tune the dielectric dipole coupling between the qubit and the resonator. The absence of additional coupling elements significantly simplifies the circuitry. No solution has been given so far to the problem of achieving independent and tunable coupling between a quantum system and two resonators.